Dtrace was, and still is, awesome. Linux has come a long way in this area in the last few years, but DTrace was one of the hottest systems management capabilities I'd seen in forever, particularly on the very large SMP systems that had become Solaris's sweet spot in those waning years.
There are reasonable criticisms of Systemtap, but a lot of Sun marketing was just bizarre. They set it up on Ubuntu (which doesn't include it, and which isn't their competitor: Red Hat is) as an example of what the setup is like. They kept complaining it was unsafe, when it was only unsafe if you wanted to use raw C for tapsets. Sun had some great tech, but they were also a sales and marketing machine that had no problems spouting garbage to make a sale.
